1. Field of the Invention
The present invention relates to a corrosion- and chipping-resistant resin coating structure for stainless steel pipes as the passageway for fluid (such as gas and liquid), especially automotive fuel and brake oil. Such stainless steel pipes are mounted under the automobile floor and are subject to corrosion by mud and chipping by splashed pebbles. The present invention is designed to completely protect them from corrosion and chipping.
2. Description of the Prior Art
Metal pipes for the fuel and brake systems are mounted under the automobile floor and are subject to corrosion and chipping by pebbles splashed by tires. Common practice for their protection has been resin coating formed in the following way. For example, a steel pipe (with an optional surface copper layer) is coated with a zinc plating layer and chromate film and then covered with a heat-shrinkable tube of polyvinyl chloride resin or polyolefin resin. Alternatively, the zinc plating layer and chromate film are covered with an intermediate layer of fluoroplastic and an adhesive layer of polyamide resin (particularly nylon 12) on which is slipped a heat-shrinkable tube of polyvinyl chloride resin, polyolefin resin, or fluoroplastic, or on which a gelled lining film is formed from polyvinyl chloride resin. (See Japanese Patent Application Nos. 212255/1988 and 26391/1990.)
A disadvantage of the conventional coating structure mentioned above is that it requires that the ends of the metal pipe be stripped off the heat-shrinkable plastic tube so as to facilitate the insertion of flared fitting and hence the exposed ends are subject to corrosion and chipping. In the case where lining film is formed instead of covering with a heat-shrinkable film, it is necessary to preliminarily mask the ends of the metal pipe.